/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

#ifndef PEBBLE_RPC_PROCESSOR_PROCESSOR_H
#define PEBBLE_RPC_PROCESSOR_PROCESSOR_H

#include <string>
#include "source/rpc/protocol/protocol.h"
#include <tr1/memory>

namespace pebble { namespace rpc { namespace processor {

/**
 * Virtual interface class that can handle events from the processor. To
 * use this you should subclass it and implement the methods that you care
 * about. Your subclass can also store local data that you may care about,
 * such as additional "arguments" to these methods (stored in the object
 * instance's state).
 */
class TProcessorEventHandler {
public:
    virtual ~TProcessorEventHandler() {}

    /**
     * Called before calling other callback methods.
     * Expected to return some sort of context object.
     * The return value is passed to all other callbacks
     * for that function invocation.
     */
    virtual void* getContext(const char* fn_name, void* serverContext) {
        (void) fn_name;
        (void) serverContext;
        return NULL;
    }

    /**
     * Expected to free resources associated with a context.
     */
    virtual void freeContext(void* ctx, const char* fn_name) {
        (void) ctx;
        (void) fn_name;
    }

    /**
     * Called before reading arguments.
     */
    virtual void preRead(void* ctx, const char* fn_name) {
        (void) ctx;
        (void) fn_name;
    }

    /**
     * Called between reading arguments and calling the handler.
     */
    virtual void postRead(void* ctx, const char* fn_name, uint32_t bytes) {
        (void) ctx;
        (void) fn_name;
        (void) bytes;
    }

    /**
     * Called between calling the handler and writing the response.
     */
    virtual void preWrite(void* ctx, const char* fn_name) {
        (void) ctx;
        (void) fn_name;
    }

    /**
     * Called after writing the response.
     */
    virtual void postWrite(void* ctx, const char* fn_name, uint32_t bytes) {
        (void) ctx;
        (void) fn_name;
        (void) bytes;
    }

    /**
     * Called when an async function call completes successfully.
     */
    virtual void asyncComplete(void* ctx, const char* fn_name) {
        (void) ctx;
        (void) fn_name;
    }

    /**
     * Called if the handler throws an undeclared exception.
     */
    virtual void handlerError(void* ctx, const char* fn_name) {
        (void) ctx;
        (void) fn_name;
    }

protected:
    TProcessorEventHandler() {}
};

/**
 * A helper class used by the generated code to free each context.
 */
class TProcessorContextFreer {
public:
    TProcessorContextFreer(TProcessorEventHandler* handler, void* context, const char* method) :
        handler_(handler), context_(context), method_(method) {}
    ~TProcessorContextFreer() { if (handler_ != NULL) handler_->freeContext(context_, method_); }
    void unregister() { handler_ = NULL; }
private:
    TProcessorEventHandler* handler_;
    void* context_;
    const char* method_;
};

/**
 * A processor is a generic object that acts upon two streams of data, one
 * an input and the other an output. The definition of this object is loose,
 * though the typical case is for some sort of server that either generates
 * responses to an input stream or forwards data from one pipe onto another.
 *
 */
class TProcessor {
public:
    virtual ~TProcessor() {}

    virtual std::string getServiceName() { return std::string(""); }

    virtual bool process(cxx::shared_ptr<protocol::TProtocol> in,
                            cxx::shared_ptr<protocol::TProtocol> out,
                            void* connectionContext) = 0;

    bool process(cxx::shared_ptr<protocol::TProtocol> io,
        void* connectionContext = NULL) {
        return process(io, io, connectionContext);
    }

    cxx::shared_ptr<TProcessorEventHandler> getEventHandler() {
        return eventHandler_;
    }

    void setEventHandler(cxx::shared_ptr<TProcessorEventHandler> eventHandler) {
        eventHandler_ = eventHandler;
    }

protected:
    TProcessor() {}

    cxx::shared_ptr<TProcessorEventHandler> eventHandler_;
};

/**
 * This is a helper class to allow boost::shared_ptr to be used with handler
 * pointers returned by the generated handler factories.
 *
 * The handler factory classes generated by the thrift compiler return raw
 * pointers, and factory->releaseHandler() must be called when the handler is
 * no longer needed.
 *
 * A ReleaseHandler object can be instantiated and passed as the second
 * parameter to a shared_ptr, so that factory->releaseHandler() will be called
 * when the object is no longer needed, instead of deleting the pointer.
 */
template<typename HandlerFactory_>
class ReleaseHandler {
public:
    explicit ReleaseHandler(const cxx::shared_ptr<HandlerFactory_>& handlerFactory) :
        handlerFactory_(handlerFactory) {}

    void operator()(typename HandlerFactory_::Handler* handler) {
        if (handler) {
            handlerFactory_->releaseHandler(handler);
        }
    }

private:
    cxx::shared_ptr<HandlerFactory_> handlerFactory_;
};

struct TConnectionInfo {
    // The input and output protocols
    cxx::shared_ptr<protocol::TProtocol> input;
    cxx::shared_ptr<protocol::TProtocol> output;
    // The underlying transport used for the connection
    // This is the transport that was returned by TServerTransport::accept(),
    // and it may be different than the transport pointed to by the input and
    // output protocols.
    cxx::shared_ptr<transport::TTransport> transport;
};

class TProcessorFactory {
public:
    virtual ~TProcessorFactory() {}

    /**
     * Get the TProcessor to use for a particular connection.
     *
     * This method is always invoked in the same thread that the connection was
     * accepted on.  This generally means that this call does not need to be
     * thread safe, as it will always be invoked from a single thread.
     */
    virtual cxx::shared_ptr<TProcessor> getProcessor(
        const TConnectionInfo& connInfo) = 0;
};

class TSingletonProcessorFactory : public TProcessorFactory {
public:
    explicit TSingletonProcessorFactory(cxx::shared_ptr<TProcessor> processor) :
        processor_(processor) {}

    cxx::shared_ptr<TProcessor> getProcessor(const TConnectionInfo&) {
        return processor_;
    }

private:
    cxx::shared_ptr<TProcessor> processor_;
};

} // namespace processor
} // namespace rpc
} // namespace pebble

#endif // PEBBLE_RPC_PROCESSOR_PROCESSOR_H
